One type of lead acid flooded or VLA battery is known as a flat plate or flat-plate deep cycle battery (or more simply, a “flat-plate battery”). These batteries are often employed in high-temperature and partial charge applications, such as found in inverters, photo-voltaic systems, and the like. When used for deep cycling applications, flat-plate stationary batteries tend to remain under charged or in a partial state of charge. Accordingly, the battery's efficiency and/or charge time diminishes over the life of the battery. Under such operating conditions, the battery plates deteriorate due to sulphation (or sulfation), and the battery life ends prematurely. Furthermore, under the typical float charging voltage, for instance, about 13.8V to 14.4V, flat-plate deep cycle batteries do not fully recover after a deep discharge. However, simply increasing the float charging voltage is not a general solution, because higher voltages accelerate the corrosion of the grid and may reduce cycle life.
In deep cycling applications such as inverter batteries, the key requirements include better re-chargeability, improved backup time, as well as lower water loss to reduce maintenance needs. However, improvement of one criteria can be accompanied by a corresponding deleterious effect to another aspect of battery performance. For example, while it is possible to reduce the water loss in a battery with certain coatings, battery charge acceptance is usually compromised by the coating process.
In some instances, such as in U.S. Pat. No. 6,703,161 owned by Daramic, LLC of Charlotte, N.C., which is incorporated by reference herein in its entirety, there have been disclosed battery separators for lead acid storage batteries that are, for instance, multi-layer battery separators.
There is a need for at least certain applications or batteries for an improved separator that overcomes the aforementioned problems, for deep cycle batteries having improved re-chargeability under float charging conditions, or for deep cycle batteries having reduced rates of water loss and grid corrosion.